In a Wideband Code-Division Multiple Access (WCDMA, Wideband Code-Division Multiple Access) system, an HSUPA technology is introduced, and uplink high-speed data transmission is implemented through a series of key technologies.
The method for controlling quality of service (QoS, Quality of Service) in HSUPA is: setting a fixed parameter “target number of retransmissions”, to make the average number of retransmissions (NHR, Number of HARQ Retransmissions) of the service converge at the “target number of retransmissions”.
The retransmission method used here is a Hybrid Automatic Repeat Request (HARQ, Hybrid Automatic Repeat Request). In the HARQ retransmission, an acknowledgement mechanism is used.
In the prior art, the configuration of the “target number of retransmissions” is generally fixed. When the “target number of retransmissions” is configured to be a small value, because the number of HARQ retransmissions is small, for a UE which is located in the center of a cell of which the load is light, the transmission rate may approach or reach the utmost rate (namely, the maximum theoretic transmission rate) with rapid increase of the physical-layer rate. However, for the UE located at the edge of coverage of the cell, the transmission power tends to be limited. In this case, when the number of HARQ retransmissions is small, a large transport block (TB, Transport Block) cannot be sent, and the transmission rate of the UE may decrease obviously, which may affect the UE experience. Besides, for a heavy-loaded cell, as limited by the load, the transmission rate of the UE cannot be improved. In this case, if a great “target number of retransmissions” is configured and power efficiency is improved by accomplishing diversity gain, the transmission rate of the UE at the edge of coverage of the cell and the transmission rate of the UE in heavy-loaded cells may still be improved. It can be seen that, the capacity of the cell configured with a smaller “target number of retransmissions” is also limited.
When the “target number of retransmissions” is configured to be a large value, for the UE that suffers limited transmission power because the UE is located at the edge of coverage of the cell, and for the UE in a heavy-loaded cell, due to a larger number of HARQ retransmissions of the UE, diversity gain can be obtained, higher power efficiency can be accomplished, the amount of data transmitted by such UEs is increased, and the capacity of the cell is increased. However, when the load of the cell is light, the physical-layer rate of the UE located at the center of the cell can approach or reach the maximum theoretic transmission rate quickly, but due to frequent HARQ retransmissions, the effective transmission rate of the UE located at the center of the light-loaded cell cannot reach the maximum value. Moreover, with sharp decrease of the number of retransmissions, the user experience is affected.